Production of finely-divided materials



Patented Oct. 31, 1922.

UNITED STATES,

H 1,433,732 PATENT OFFICE.

WARREN K. LEWIS AND ROBERT E. WILSON, OF CAMBRIDGE, MASSACHUSETTS.

PRODUCTION OF FINELY-DIVIDED MATERIALS.

Ho Drawing. Application filed November- To all whom it may concern:

Be it knownthat we, WARREN K. LEWIS and ROBERT E. WILsoN, of Cambridge, Massachusetts, citizens of the United States, have invented new and useful Improvements in the Production of Finely-Divided Materials, of which the following is a specification.

' This invention relates to the production of materials in very finely divided particles and more especially to the production of clouds or mists. f

Artificial smoke clouds or fogs find extensive use in warfare to conceal various move ments fromv the enemy. Such clouds are especially adapted to conceal moving Vessels from submarinesseeking to attack them and also to conceal preparations for surprise attacks upon the enemys lines. A 3

Among the objects of this inventionis the production of a cloudfmist pr fog which will have a high total obscuring power, high density, low rate of settling' and great stability. This invention comprises producing a cloud or fog by the ihteractiorrof two or more? substances in the liquid orf -gaseous .state to form liquid or solid particles difvaporization can be employed.

fused through an inert medium. When two or more gaseous substances, capable of reacting to form a liquid or a solid, are

brought together in highly diluted form, a

very stable and dense cloud of high obscuring power is formed. Furthermore, when a chloride, such as silicon or titanium tetra-' chloride is diluted with a large volume of moist air and then brou ht into contact with ammonia gas, a very' ense, permanent cloud is formed.

'A satisfactory smoke cloud requires, in the first place, density, i. e., a relatively thin layer of smoke must completely obscure any object behind it. In the secbnd place, the cloud must be stable, i. e.,it mustnot dissipate itself on standin or dilution nor must it settle out. Thi-r -,}.the cloud must be easily produced without complicated apparatus or diificulties of manipulation.- Also the materials required for producing the cloudmust be readily available,-preferably cheap,easily transported and not dangerous to-handle.

By. a 'series of experiments, the following conditions adapted for the production of permanent smoke clouds;

1..Only' gases or substances capable of have been determined best 10, 1920. Serial No. 423,174.

2. The substances from which the smoke 18 to be produced should be brought into the gaseous or vapor state before reacting to form the cloud.

3. The gases or vapors should be diluted 'w1th some inert gas, preferably air, before interaction. The degree ot dilution essential forthe best results must be determined for each specific gas. It has, however, been (c) Inactiveespecially towards water,

- otherwise, the particles 'wi'll tend to grow by condensation of water into them, es-

pecially in humid atmosphere.

The reacting substances from which the smoke is to beproduced should, if possible, be condensed gases having low heat or vaporization. Such liquids will tend to vaporize readily upon relief of pressure and maintain a constant pressure until their evaporation is complete. In this respect, they possess a great advantage over compressed gases, the pressure of which decreases constantly upon use.v

Any cloud fulfilling these requirements "must be made up of extremely small particles of liquid or solid, dispersed in the air. I The individual particles must be large enough to disperse 'or' diffuse light, but

-otheiwise the smaller the particles the" greater the obscuring power and the more stable the cloud, for agiven concentration of cloud in air.

enough to diffuse 1: ght at all. The pro .lem of cloudformatiomtherefore, reduces comes in contact with hydrochloric 'acidgas,

The difi'using power of a given particle is probably not greatly influenced by its size if the particle is'large a cloud of ammonium chloride is formed,

lthe cloud having a rather poor obscuring itself to the'problem of producing a 'sus-@ i but slightly after 100 volumes of air have power. -From experience with ammonium chloride. it was felt that this must be due to a. formation of the fume under unsatisfactory conditions and, therefore, experimental investigation of the" optical properties ofammonium chloride clouds, as determined by the conditions under which they are formed, was undertaken.

The obscuring power of a smoke was measured by determining the distance in feet beyond which it was impossible to see the filament of a standard electric light bulb. The density of clouds formed by adding a mixture of hydrochloric acid and ammonium gases, each diluted to an equal degree with air, was first determined. The maximum density of the cloud occurs when a volume of air about times that of the reacting gases is used. The density is measured by the reciprocal of the number of feet thickness necessaryto completely obscure the light filament. A cloud formed by ammonia and hydrochloric acid diluted sixty fold with air is many times as dense as a cloud formed by interaction between the undiluted gases. The efficiency of the cloud is therefore much greater and it is only possible to secure the production of a satisfactory cloud from these two gases v the reaction chamber wlth the SlCl, and the by diluting them before this interaction.

This matter of cloud density is,- however, only one of the factors of obscuring power: It is obvious that a layer of two feet thickness of a given cloud will have more obscuring power-probably twice the obscuring powerwhich a. layer of. 1 foot thickness would have. In other words, a total obscurin power (T. O. P.) of a cloud is measured by its cloud density times its volume. This product of clouddensity in re- 1 ciprocal feet times its volume in cubic feet is therefore the measure of the effectiveness of a cloud. The total obscuring power does not go through a maximum in this case but approaches a limiting value'which increases been used for dilution. -To secure the optimum resultsfrom an ammonium chloride cloud, at least this volume of 'diluent'air must be employed. M

The experiments above set forth were made by interaction of hydrochloric acid and ammonia both of which were, diluted with equal volumes of air. effect of dilution of one of these gases over that of' the other, a series of clouds were made, using in all cases the same total amount of air as diluent but varying the proportions in which the air wasdistributed between the ammonia and thehydrochloric acid. The density curve wasfound to go through a distinct maximum when both gases are diluted, indicating that dilution of both gases is better than dilution of one alone. On the other hand, the advantage gained'by In order to determine the the dilution of both gases is not very great and if the dilution of one alone is much simpler, it may be advisable to sacrifice the small advantage of increase in density by diluting both gases.

The following combinations of smoke producing substances have been found to give fairl satisfactory resultsz SO +NH,; SnClZ-l-NH,; SnCh-l-NHH-I-LO; POLA- NH +H O; Cl -l-NH SiCl,+NH SiCl +NH +H O; TiCl +NH +H O; $0 01 P+'O TiClA-I-I O. Of these the cloud produced by interaction of SiCh+NH H O most nearly fulfils the conditions which have been found best suited for the production of clouds.

When moist air and NH mix with SiCl at the same time, a part of the SiCl combines with the NH directly, and part hydrolizes in the moist air, and the resultant HCl combines with the NH Since the SiChfiNH particles formed are known to have less T. O.'P. per pound than NH,C1 particles, it is obviously best to encourage the formation of the latter. In order to bring this about, two runs were made in one of which the NH and the \moist air NH, was put into the mixing chamber farther below. This latter method gave the best results, and although it would be eX- pected'that when hydrolysis took place in this way, 1SiCl, would require but 4NH it was found that 5NI-I gave slightly better results in practice, probably due to the formation even under these conditions of some SiCl .6NI-I 1 The fact that the T. O. P. is very high, the curve flat, the tip distance (the distance between the nozzles emitting the reacting substance) and other details quite unimportant, make this the most desirable smoke thus far produced. While SiCl is a liquid and hence undesirable in some ways, its high volatility (B. P. 57 (1.), the absence of corrosive-properties, or any great tendency to hm up with moist air, are all points in its .avor. It can be placed in steamjacketed steel tanks and used as a gas, or forced out by the pressure of some liquified gas, such as C0,, in the same cylinder. I

Titanium tetrachloride has also .been found to. produce a good cloud, but th'e liquid TiCl clogs more readily and the tip distance is important, whereas with SiCl, the tip distance is unimportant. The boiling point of TiCl is about 130 C., which is much-higher than that of Sick, and hence its vaporization is more difficult. It is also more expensive and usually more difficult to obtain. While this invention has been described as applied tothe production of smoke clouds,it is not intended that it be" limited to the same since the method herein disclosed is readily applicable to which may be effected therein without de-- arting from the spirit and scope of this invention, it is desired that only such limitations vbe imposed as are indicated in the appended claims.

We claim as our invention:

1. In a method of producing finely divided materials, diluting all the components with an inert gaseous substance and mixing.

2. In a method of producing finely divided materials,- diluting the components with moist inert gaseous substance and then mix-' ing.

3. In a method of producing finely divided materials, diluting the components with moist air and then mixing.

4. In a method of producing finely divided materials, diluting one of the components to ahigh degree with an inert gaseous substance and then mixing.

chloride, diluting same with a large volume of an inert gaseous substance and then treat-5}? H t highly diluted with air.

5.- In a method of producing finely divided materials, diluting the components to a high degree with an inert gaseous substance and then mixing. t

6. In a method of producing finely divided, materials, diluting the components to a high degree with'air and then mixing.-

7. In .a method of producingfinely divided materials, diluting the componentsto a high degree with moist .inert gaseous substance and then mixing 8. In a method of producing finely divided materials, diluting the components to a'high degree withmoist air and then mixing.

9. In a method of producing finely divided materials, mixing a chloride of an element of the fourth group of the periodic table,

whose atomic weight is 25-100, with ammonia; f

l0. Ingfa method of producing finelydivided materials, mixing a chloride of an element of the fourth group of.'.tl ieperiodic table, whose atomic weightis'g2l5 -l00, with" a large volume of moist air and thei with ammonia. i

11. A process comprising volatilizing a ing the resulting mixture" with a substancecapable of reacting therewith to produce finely divided material possessing high stability'and permanency.

-12.-A process comprising volatilizing a chloride, diluting same with a large volume high stability and permanency.

of an inert gaseous substance and then treating the resulting mixture with ammonia.

13. A process comprising volatilizing a chloride of an element of the fourth group of the periodic table having an atomic weight 25400, diluting same with a large volume of an inert gaseous substance and then treating the resulting mixture with a substance capable of reacting therewith to' produce finely divided material possessing 14. ,A process comprising volatilizing a chloride of an element of the fourth group of the periodic table having an atomic weight 25-100, diluting same with a large volume of an inert gaseous substance and their treating the resulting mixture with ammonia. s

15. A process comprising volatilizing a chloride of an element of the fourth group of the periodic table having an atomic weight 25-100, diluting same with a large I volume of moist air and then treating the resulting mixture with a substance capable of reacting therewith to produce finely divided material possessing high stability andfpermanency.

chloride of am element of the fourth group of the periodic table having an atomic weight 25-100, diluting same with at least;

100 times its volume of air and then mixing same with ammonia. j

17. A process comprising volatilizing a chloride of an element of the fourth group of the periodic table having an atomic weight 25-100, diluting same with at least 16. A process comprising volatilizing a i times its volume of moist air and then mixing same with ammonia.

18. In a method of producing finely divided materials, mixing SiCl with ammonia.

19. In a method of producing finelydivided materials, diluting SiCl, with air and then mixing with ammonia. 20. In" a method of producing finely divided materials, diluting SiCl, with moist. air and then mixing with ammonia.

21'. In a method. of producing finely divided. materials, diluting SiCl with a least 100 times 'its volume of .moist air and mixing same with ammonia.

E23.v In I a'method of producing a cloud, mixing a volatile chloride with ammonia, at

east one of said substances being previously 24. A cloud comprising the reaction prodtable having an atomic weight less than 100.

large volume of moist'air and then mixing 7 nets of ammonia and a chloride of; an elemnt of the fourth group of'the periodic nets of ammonia-and a chloride of an element of the fourth group of the periodic tablehaving an atomicweight 25100 and highly dispersed in inert gaseous substance.

26. A cloud having great stability, high 7 density, low rate of settling and high total obscuring power and comprlsing the reaction products of ammonia and a chloride of an element oi the fourth group of the periodic table having an atomic weight 25-400 and highly dispersed in air.

27. A cloud comprising the reaction products of ammonia and a chloride of an element of the fourth group of the periodic table having an atomic weight of 25-100 and highly dispersed in moist air.

'28. A' cloud having great stability, high density, low rate of settling and high total obscuring power and c ontalning very finely divided particles comprising the reaction products of silicon tetrachloride and ammonia.

29. A cloud containing very finely divided. particles comprising the reaction products of ammonia and silicon tetrachloride highly. diluted with moist air.

30. Finely divided material comprising the reaction products of components, all of said components being dispersed with inertgaseous material before reaction.

31. Finely divided material comprising the reaction products of components, some of said components being highly dispersed with inert gaseous material beforereaction.

32. Finely divided material comprising 35 the reaction products of components,.all of said components being highly dispersed with inert gaseous material before reaction.

33.'Finely divided material comprising the reaction products of components, all of 40 said components being dispersed with air before reaction.

34. Finely divided material comprising the reaction products of components, some of said components being highly dispersed'45 with air before reaction. A

35. Finely divided material comprisin the reaction products of components, all 0 i said components being highly dispersed with air before reaction.

WARREN K. LEWIS. ROBERT E. WILSON.

, Certificate of Correction. I v It is herebyce'rtified that in Letters Patent No.1,433,732,gifanted Qctober 31,

,1922, upon the applicatipn of Warren Lewis bridge, Massachusetts, for an improvement Materia1s, errors a ipear the printed specification'requiring correction.a ;f lows: Page 1, line 85, {time word I or? rea l e e 2, ammonium read am mom'a; page 3, liner 129, claim 24, for the words i00 read 25- 100; and that the said Letters Patent ghoul and Wilson," oifYCam{ ""Production bf Finely-Divided line, 15; for. the word less' than d be readl with these corrections therein that the same may conform to the recin il of the in the Patent Oflieef 

